internal order

hi,

"Internal order is temporary in nature where you want to capture costs for some temporary purpose. Finally, you may settle these costs to some assets, CO objects,etc."

1) which module this internal order originating from?

2) how to use internal order?

3) what does it mean by internal order settlement rule?

4) what would happen before and after the settlement rule applied?

5) why can use internal order in asset management?

6) what is CO object?

thanks